Industrial and power generation gas turbines have control systems or controllers that monitor and control the operation of the gas turbine. These controllers govern the combustion system of the gas turbine. Gas turbines require precise fuel delivery to achieve fuel-lean homogenous mixing of the fuel and air in each local combustion zone, which is necessary to operate at required low emission levels. Gas turbines must maintain an operating margin above a lean blowout limit. Finely tuned control of local combustion is necessary to maintain flame stability in the turbine combustors without compromising performance in advanced turbines.
In the current gas turbines, if one combustor, or combustion can. loses flame, then the exhaust thermocouples recognize the elevated temperature differences between the extinguished combustion can and the other combustion cans, and the control system reacts by shutting down the turbine. Such controls may result in a prolonged outage and the loss of operating time and revenue. In current gas turbine control systems certain signals can be used to detect an extinguished combustion can that are faster than the exhaust thermocouple signals, due to the relatively slow nature of the transport delay time from the combustion can to the exhaust thermocouple, and the subsequent heat transfer and temperature change in the thermocouple.
When the load drop is detected the gas turbine, under the current control system, the control system will deliver more fuel into the system to try to increase load. When a combustion can blows out, or its flame is extinguished, fuel nozzles that are nearest to the cross-fire tubes are operating fuel lean and their flame is weak and positioned further downstream of the cross-fire tube. Delivering more fuel into the combustion can in this state may be inadequate to promote cross-fire into the extinguished combustor can. However, adjusting the divisions of fuel and enriching the fuel mixture in the fuel nozzles will promote cross-fire into the unlit combustion can.
An algorithm is needed so that the control system may perform a fuel adjustment very rapidly, such that cross-fire occurs to ignite the extinguished combustion can, and at the same time span is short enough to minimize the impact in the operation or emissions of the gas turbine.
What is needed is a controller that detects an extinguished combustion can using a faster signal, e.g., load, within that transport delay time, modulate the division of fuel between combustion fuel nozzles in each combustion can and hold until the controller detects a load recovery.